Safety means for protecting internal combustion engines upon loss of oil pressure



Jan. 7, 1964 SAFETY MEANS FOR PROTECTING INTERNAL COMBUSTION T CROWE 3,116,729

ENGINES UPON LOSS OF OIL PRESSURE Filed April 25, 1961 QB I """" II I i I Inventor 72 0/1443 Crow 5 By d. I

Attorney United States Patent SAFETY MEANS FQR PROTECTING INTERNAL COMBUSTION ENGINES UPON LOSS OF OIL PRESSURE Thomas Crowe, Asireaton, Qounty Limerick, Ireland Filed Apr. 25, 1961, Ser. No. 105,466 Claims priority, application Great Britain Aug. 31, 1960 4 Claims. (Cl. 123-179) This invention concerns means for preventing damage to internal combustion engines in the event of a failure of the 'oil pressure system, its object being to provide relatively simple safety means, reliable in operation, which will automatically stop the engine if the oil pressure falls below a predetermined minimum during normal running. In order to be of practical use the safety means must also be such as to permit the starting of the engine, even when the oil pressure is Zero, but to ensure that the engine is stopped before damage occurs if the pressure does not build up to a certain value within a very short period of time.

These desiderata are attained by the safety means according to the invention which comprises an electric circuit including two pairs of contacts, one pair of contacts being controlled by a device responsive to the oil pressure of the engine to which the safety means are applied while the second pair of contacts is controlled by an electrically actuated time switch adapted to be energised so as to open said last mentioned contacts simultaneously with the operation of the engine starter but to close same after a predetermined time interval, said circuit being adapted to be closed only when both pairs of contacts are closed, and an engine-immobilising device responsive to the closing of said circuit.

In the case of internal combustion engines having a coil-ignition system the immobilising of the engine may be readily brought about by the closing of a grounding circuit associated with the output side of the coil. If desired, however, the immobilising of the engine may be brought about by cutting off the fuel supply, this method being suitable, for example, for diesel type oil engines. In the latter case the simultaneous closing of the two pairs of contacts above mentioned is adapted to actuate a relay controlling the circuit of a solenoid, the armature of which is operatively connected with a fuel cut-out device, for example, by a Bowden wire control.

The invention is hereinafter described with reference to the accompanying drawings which show two examples of electric circuits for carrying out the invention, and wherein:

FIG. 1 is a diagram showing the invention applied to the coil-ignition system of an internal combustion engine, and

FIG. 2 is a diagram showing the manner in which the invention may be applied to control the fuel supply to an engine.

Like parts are indicated by similar reference numerals in both figures.

It will be understood that only parts essential to the invention are shown in the drawings, this being adequate for a full understanding of the invention and to enable it to be readily carried into practice.

Referring to FIG. 1, the diagram shows the starter 1 for an internal combustion engine, a starter battery 2 and starter switch 3, all as commonly found in starting arrangements for internal combustion engines. With engines of this kind operating with spark-ignition a device for producing the high-tension current required for the spark is necessary, this device being normally either a transformer coil or a magneto. In FIG. 1 a coil 4 is represented, the remaining details of the ignition sysu aiiaiza Patented Jan. 7, 1984 "ice tern not being shown as they are well-known and have no bearing upon the invention.

The secondary or output-side of the coil 4 is connected to ground through two switches 5 and 6 arranged in series. The switch 5 is a so-called time switch advantageously comprising a solenoid 7 connected with a dashpot device 8. The winding of the solenoid 7 is in circuit with the starter 1 and is energised so as to open the contacts of switch 5 (as indicated by broken lines in FIG. 1) when the starter circuit is closed by closure of the starter switch 3.

After operation of the solenoid 7 and subsequent deenergising of the solenoid circuit when the starter switch is released the switch 5 will remain open for a predetermined period, advantageously about seven seconds, but will close slowly under the influence of the dash-pot device 8. Any known form of time-switch that will operate in the manner described may obviously be employed in carrying out the invention.

The switch 6 is operatively connected with a pressureresponsive device 9. The latter preferably takes the form of a chamber '10 which communicates by way of a pipe 11 with the pressure lubrication system of the engine and has a diaphragm '12 operatively connected with the switch 6. Many automobiles, for example, are customarily fitted with a diaphragm-operated switch of this kind in circuit with a warning light which shows when the oil pressure drops to a predetermined minimum, and in such case the existing diaphragm-operated switch may be connected in the grounding circuit of the coil 4 as above described when applying the invention to the automobile in question. In the latter event the only device required in order to apply the invention to the existing engine is the time switch-5, 7, 8, which may advantageously be supplied as a boxed unit (indicated by the chain line 18) only requiring the appropriate electrical connections to apply it to the existing engine.

It will be evident that with the arrangement described, upon the starter 1 being energised, the solenoid 7 is also energised to open the switch 5. The switch 5 closes slowly under the influence of the device 8 and during the few seconds delay thereby occasioned the oil pressure of the engine can build up, if the oil system is functioning properly, thereby opening the switch 6. If the switch 6 remains closed, however, due to a fault in the oil system, the coil 4 will :be grounded upon closing of the time switch 5, thereby shorting out an essential portion of the ignition system and stopping the engine. Similarly, if the oil pressure fails at any time during operation of the engine, the switch 6 will close and automatically stop the engine.

Instead of being applied to the ignition system of the engine, the invention may equally be applied to the fuel supply system so as to stop the engine by cutting off the fuel supply it the oil pressure fails. An arrangement for this purpose is shown in FIG. 2, wherein the starter 1, starter switch 3 and battery 2 as well as the time switch device 5, 7, 8 and oil pressure-controlled switch device 6, 9, 10 are substantially the same as described above with reference to FIG. 1. Instead of being arranged in the grounding circuit of an ignition coil, however, the switches 5 and 6 are arranged in the energising circuit of a relay 13. Operation of the latter is adapted to close the circuit of a solenoid 14 the armature of which is operatively connected to a valve 15 controlling the fuel supply to the engine. A main switch 16 which must be closed before starting the engine is preferably incorporated in the circuit of the relay.

The operation of the arrangement shown in FIG. 2 is substantially similar to that shown in FIG. 1 in that, upon starting the engine, the switch 5 is opened for a limited time during which the switch 6 will also open if the oil pressure builds up to a predetermined value; the switch 5 then closes. Should the oil pressure fail, the switch 6 will close, and the switch 5 also being closed the relay 13 will operate, thus closing the circuit of the solenoid 14 which moves the cut-off valve 15 to interrupt the fuel supply to the engine and bring it to a stop before damage due to lack of lubrication can occur.

For application to diesel-type engines, for example, the devices required to apply the invention, namely the time switch 5, '7, 8, relay 13 and solenoid 14 may be conveniently mounted together in a box as indicated by the chain-dotted line 117.

From the foregoing it will be evident that the invention may be carried out in a number of practical forms, modifications being made as will be obvious to those skilled in the art to meet the practical circumstances or details of the particular engine to which the invention is to be applied.

I claim:

1. For an intern-a1 combustion engine having an electric starter, an engine immobilising device, an electric circuit for operating said device on closure of said circuit, a pair of switches arranged in series in said circuit, means responsive to the fluid pressure in the engine lubrication system for opening and closing one of said switches in response to a predetermined increase or decrease, respectively, in said pressure, means for opening the second of said switches upon closure of the engine starter circuit and delayed action means for automatically closing said last-mentioned switch upon the opening of the starter circuit.

2. For an internal combustion engine having an electric starter, an electric spark ignition system, a grounding circuit for said ignition system, a pair of switches arranged in series in said circuit, switch operating means connected wth one of said switches for opening and closing said one switch in response to a predetermined increase and decrease, respectively, in the fluid pressure of the engine lubrication system, a solenoid in the engine starter circuit for opening the other of said switches upon closure of the starter circuit, a dash-pot device, and means for automatically closing the last-mentioned switch against the delaying action of the dash-pot device upon de-energising of the starter circuit.

3. For an internal combustion engine having an electric starter, means for controlling fuel admission comprising a fuel valve operating member, a solenoid operatively associated therewith, a relay controlling the operation of said solenoid, and an energising circuit for said relay including a pair of switches arranged in series in said circuit, means responsive to the fluid pressure in the engine lubrication system for opening and closing one of said switches in response to a predetermined increase and decrease, respectively, in said pressure, means for opening the second of said switches upon closure of the engine starter circuit and delayed-action means for automatically closing said last-mentioned switch upon the opening of the starter circuit.

4. For an internal combustion engine having an electric starter, means for controlling fuel admission comprising a fuel valve operating member, a solenoid operatively associated therewith, a relay controlling the operation of said solenoid, and an energising circuit for said relay including a pair of switches arranged in series in said circuit, switch operating means connected with one of said switches for opening and closing same in response to predetermined increase and decrease, respectively, in the fluid pressure of the engine lubrication system, a solenoid in the engine starter circuit for opening the other of said switches upon closure of the starter circuit, a dashpot device, and means for automatically closing the lastmentioned switch against the delaying action of the dashpot device upon de-energising of the starter circuit.

References Cited in the file of this patent UNITED STATES PATENTS 2,504,670 Everest Apr. 18, 1950 2,537,354 Korte et a1. Jan. 9, 1951 2,609,809 Parker Sept. 9, 1952 2,725,867 Steberl Dec. 6, 1955 2,768,708 Cooper Oct. 30, 1956 2,866,908 Cromwell Dec. 30, 1958 2,892,454 Cheetham June 30, 1959 

1. FOR AN INTERNAL COMBUSTION ENGINE HAVING AN ELECTRIC STARTER, AN ENGINE IMMOBILISING DEVICE, AN ELECTRIC CIRCUIT FOR OPERATING SAID DEVICE ON CLOSURE OF SAID CIRCUIT, A PAIR OF SWITCHES ARRANGED IN SERIES IN SAID CIRCUIT, MEANS RESPONSIVE TO THE FLUID PRESSURE IN THE ENGINE LUBRICATION SYSTEM FOR OPENING AND CLOSING ONE OF SAID SWITCHES IN RESPONSE TO A PREDETERMINED INCREASE OR DECREASE, RESPECTIVELY, IN SAID PRESSURE, MEANS FOR OPENING THE SECOND OF SAID SWITCHES UPON CLOSURE OF THE ENGINE STARTER CIRCUIT AND DELAYED ACTION MEANS FOR AUTOMATICALLY CLOSING SAID LAST-MENTIONED SWITCH UPON THE OPENING OF THE STARTER CIRCUIT. 